In the traditional cellular communication technologies, a flow of data communication between two User Equipments (UEs) is as illustrated in FIG. 1. Voice, data and other traffic between the two UEs are exchanged through evolved NodeBs (eNBs) where they reside, and a core network.
The technology of Device to Device (D2D), namely a technology of D2D direct communication, refers to that data can be transmitted between adjacent UEs in a short-distance range over a direct link without being forwarded by a central node (i.e., a base station), as illustrated in FIG. 2. The D2D technology has the following advantages due to its short-distance communication characteristic and direct communication scheme:
The UEs can communicate directly with each other over a short distance at a higher data rate, with a lower delay, and with lower power consumption;
Spectrum resources can be accessed efficiently by the UEs widely distributed in a network due to the short-distance characteristic of the D2D communication link;
The D2D direct communication scheme can accommodate a demand of services, e.g., Peer to Peer (P2P) and other services, for sharing local data to thereby provide data services which can be adapted flexibly; and
A coverage area of the network can be extended in D2D direct communication using a large number of communication UEs widely distributed in the network.
The Long Term Evolution (LTE) D2D technology refers to D2D communication via the LTE licensed frequency band controlled by an LTE network On one hand, the advantages of the D2D technology can be fully utilized, and on the other hand, some problems of the traditional D2D technology, e.g., uncontrollable interference, etc., can be overcome due to the control by the LTE network. The LTE D2D characteristic has been introduced to enable the LTE technology to evolve from the simple radio mobile cellular communication technology toward the universal connectivity technology.
For an uplink subframe/uplink carrier, a transmitting UE of the D2D link can perform transmission over an N2D link and the D2D link concurrently in the current D2D subframe, so there will be no concern with duplex transmission/reception over the D2D link and the N2D link. A receiving UE of the D2D link can not perform transmission over the N2D link and the D2D link concurrently in the current D2D subframe, so there will be a concern with duplex transmission/reception over the D2D link and the N2D link for the receiving UE of the D2D link.
In summary, there may be a concern with duplex transmission/reception over the D2D link and the N2D link for the receiving UE of the D2D link.